Numerical controller

A numerical controller that machines a workpiece by controlling a machining device including a tool based on a machining program and that carries out optimal approach of the tool in a screw thread cutting cycle, the numerical controller comprising:

• an instruction analysis unit that analyzes the machining program;
• a cycle motion start point determination unit that calculates a cycle motion start point where a screw thread cutting cycle (including a rapid traverse of X axis and a cutting feed of Z axis) is to be started toward an end face of the workpiece;
• an acceleration/deceleration control unit that moves the tool from the cycle motion start point to the screw thread cutting start point with motions of a plurality of axes overlapped;
• and
• a control unit that controls motions of the machining device based on control instructions received from the instruction analysis unit and the acceleration/deceleration control unit, wherein
• the cycle motion start point is a point from which acceleration or deceleration of a first axis parallel to a direction of the cutting feed and a second axis orthogonal to the first axis is started so as to make a speed of the first axis reach a specified cutting feed speed and to make a speed of the second axis substantially become zero at time of arrival at the screw thread cutting start point.